1. Field of the Invention
The present invention relates to the manufacturing technology of a liquid crystal display, in particular to a process for drying an alignment film material that is coated on a substrate.
2. Description of the Related Art
An alignment film is formed on a substrate of a liquid crystal display so as to make a molecular arrangement state of liquid crystal uniform. A process for forming the alignment film includes (1) printing process of an alignment film material that is diluted with a solvent on one surface of a substrate, and (2) heating process for curing the alignment film formed in the printing process.
The heating process includes preliminarily drying process for removing a solvent from the coating of alignment film material at a temperature of substantially 100 degree centigrade, and curing the preliminarily dried alignment film at a temperature equal to 180 degree centigrade or more. In the former process, a hot plate such as shown in FIG. 13 is employed. The hot plate includes a plate 15 with a plurality of through-holes 12 that lead to an outlet in an area (hereinafter referred to as a substrate contact area) that comes into contact with other surface (a surface opposite to the surface where the coating of alignment film material is formed) of the substrate 1, a heater 2 that is buried in the plate 15, and a vacuum pump (not shown in the drawing) connected to the outlet of the plate 15.
According to such a configuration, since owing to vacuum suction of the vacuum pump, the substrate 1 can be brought into close contact with the plate 15, heat from the heater 2 can be efficiently conducted through the plate 15 to the substrate 1. The coating formed on the substrate 1 is preliminarily dried by the heat.
After the heating process, the substrate 1 in close contact with the plate 15 is necessary to be transferred from the plate 15 to a transfer arm 11. Accordingly, inside of the plate 15, a plurality of thrust pins 3 for thrusting up the substrate 1 from the substrate contact area is accommodated. As shown in FIG. 14, owing to the thrust of these thrust pins 3, the substrate 1 is detached from the plate 15. As a result, between the substrate 1 and the plate 15, a gap where an arm 11 is inserted can be secured.